/*
	MALLOC DEMO #3 Illustrates:
		declaring an automatic array of pointers
		use of malloc function on that array
		use of the free function on that array
		passing pointers into functions
		the ** prototype (pointer to a pointer)
*/

#include <stdlib.h>  /* string libraries etc */
#include <stdio.h>   /* input output */
#include <string.h>

#define  MAX_WORDS    10
#define  MAX_WORDLEN  50

/*                    F U N C T I O N   P R O T O T Y P E S */

void loadArray( char **arr, char * infileName, int * count );
void printArray( char **arr, int count );
void freeArray( char **word, int count );
void fatal( char * errmsg);

                  /*   M A I N   F U N C T I O N  */

int main( int argc, char *argv[] )
{
	char *wordArray[MAX_WORDS]; /* a.k.a array of Strings */
	int wordCount=0;

	if (argc < 2 )
		fatal("Must enter a text input filename on cmd line. Exiting Program.");

	loadArray( wordArray, argv[1], &wordCount); /* pass only the array's name: it's already allocated */
	printf("Printing wordArray:\n\n");
	printArray( wordArray, wordCount ); /* again - need only pass array's name */
	freeArray( wordArray, wordCount ); /* same here */

	return EXIT_SUCCESS;
}

/* ------------------------------------------------------------------------
   Takes 3 args: the name of an array of pointers a file name to read from
   and pointer to counter of words read in. Mallocs  each pointer in the and
   copies a string into it.
*/
void loadArray( char **arr, char * infileName, int * wordCount)
{
	char buffer[MAX_WORDLEN]; /* 49 chars plus a null terminator */
	FILE * infile;


	infile = fopen( infileName, "r" );
	if (!infile)
		fatal("Can't open specified input file. Exiting Program.");

	*wordCount=0;
	/* DANGER: fscanf of string vulnerable to overflow */
	while ( (*wordCount < MAX_WORDS)  &&  fgets(buffer, MAX_WORDLEN, infile) ) /* WARNING: fgets vulnerable to truncation but not overflow */
	{
		arr[*wordCount] =  malloc( (strlen(buffer)+1) * sizeof(char) );
		if (arr[*wordCount]==NULL) /* ALWAYS CHECK FOR NULL */
			fatal("malloc failed. Exiting Program.");

		strcpy( arr[*wordCount], buffer );
		++(*wordCount);
	}
	fclose(infile);
}

/* ---------------------------------------------------------------------------
   Takes 2 args: the name of an array of pointers, and a count of how many pointers
   have been malloc'd. Prints each string.
*/
void printArray( char **arr, int wordCount )
{
	int i;
	for(i=0 ; i<wordCount; ++i)
		printf("wordArray[%d]: %s\n", i, arr[i] );
}


/* ----------------------------------------------------------------------------
   Takes 2 arg: the name of an array of pointers and acount of how many have been
   malloc'd. Visits each pointer in the array and frees the memory allocated to it.
*/
void freeArray( char **arr, int wordCount )
{
	int i;
	for(i=0 ; i<wordCount; ++i)
		free( arr[i] );
}

void fatal( char * errmsg)
{
	fprintf( stderr, "\n%s\n", errmsg );
	exit( EXIT_FAILURE ); /* a NON_ZERO value */
}